Downhole weight bearing apparatus and method

ABSTRACT

A downhole tool for connection in a work string to prevent premature activation of weight set tools on the work string. The tool has moveable pads which contact the tubing wall and thereby support the weight of the work string. The pads are activated by increasing fluid pressure in the annulus between the tool and tubing wall and deactivated by increasing fluid pressure through the central bore of the tool.

[0001] The present invention relates to downhole tools and, inparticular, though not exclusively, to a tool which supports the weightof a work string within a well bore, as typically utilised in oil andgas production.

[0002] During drilling or completion of a well, a work string comprisingconnected sections of tubing is typically inserted in the well bore.Each additional section increases the weight exerted on the string. Thisweight is required for some downhole operations such as drilling wherethe weight ensures a drill bit, mounted on the end of the work string,is held against a formation.

[0003] Additionally weight set tools have been developed which generallyoperate by landing a part of the tool on a shoulder of the tool or aformation within the well bore. The contact surface then allows the toolto bear the weight of the string, and in bearing the weight of thestring, parts within the tool are moved in relation to each other toperform a function required by the tool. Such a weight set tool, forexample, is that in UK Patent No 2272923 which describes a downhole toolfor circulating fluid. This tool includes a sleeve which engages ashoulder portion in the well bore. When engagement occurs, the weight ofthe string bears down on the tool, moving the tool in relation to thesleeve which is now static against the formation. The change inrelationship between the tool and the sleeve aligns ports between a boreof the tool and the sleeve to provide for the radial passage of fluidfrom the bore of the tool.

[0004] A disadvantage of such weight set tools are that they can beactivated prematurely whenever an apparent weight or, alternatively,contact with a formation in the well bore occurs. These conditionsgenerally prevail when the body of the tool experiences a pressuredifferential across its surface, causing the body to expandlongitudinally. A temperature differential across the body may have thesame effect, as can changes in the body dimensions caused by changesresulting from different plugs of fluids passing down the bore of thetool and up the annulus between the string and the well bore wall ortubing wall if inserted.

[0005] It is an object of at least one embodiment of the presentinvention to provide a downhole tool which prevents the prematureactivation of weight set tools mounted on a string below the device.

[0006] It is a further object of at least one embodiment of the presentinvention to provide a downhole tool which can be selectively actuatedto support at least part of the weight of a string to which it isattached.

[0007] According to a first aspect of the present invention, there isprovided a downhole tool for connection in a string to be inserted intotubing in a well bore, the tool comprising a tubular body includingmeans for attachment to the string, and a sleeve mounted on the tubularbody wherein the sleeve includes means to contact a wall of the tubing,such that the tool bears at least a part of a weight of the string.

[0008] Preferably the means for attaching the tubular body to the stringare threaded box sections.

[0009] Preferably the means to contact the tubing wall is a plurality ofmoveable pads. Preferably there are four pads. Preferably the pads arearranged to move radially with respect to the longitudinal axis of thebore.

[0010] Preferably the tubular body has inner and outer surfaces whichare substantially cylindrical. More preferably the tubular body includesone or more radial ports. Advantageously, the tubular body includes oneradial port for each moveable pad.

[0011] Preferably the sleeve has a substantially cylindrical outersurface. Preferably also the sleeve has a square cross-sectional innersurface, which is a clearance fit over the tubular body. Advantageously,the sleeve includes one or more grooves positioned longitudinally on theouter surface. Each groove allows for the passage of fluids between theouter surface of the sleeve and the inner surface of the tubing wall.

[0012] Additionally, the sleeve may include tapered upper and lowersections on the outer surface to direct fluid flow across the sleeve.

[0013] Preferably the pads include an abrasive outer surface. Theabrasive outer surface provides a large surface area with which tocontact the tubing wall. The abrasive surface also provides a bettergrip to the tubing wall, thereby ensure the sleeve is held while bearingthe weight of the string.

[0014] Preferably the tool is hydraulically operated. Thus the moveablepads can be selectively actuated to contact the wall of the tubing. Morepreferably the sleeve includes a at least one port, the port(s)providing access of fluid from the annulus between the tool and thetubing wall to a back surface of the pad.

[0015] Preferably also there is at least one second port in the sleeve,the second port(s) providing access of fluid between the radial port ofthe tubular body and a front surface of the moveable pad, such thatfluid travelling through the bore can actuate the front surface of thepad to move the pad away from the tubing wall and disengage the tool.

[0016] Preferably also the tool includes means to locate the padsagainst the tubular body. The means to locate the pads may comprise apin. More preferably the pin is a grub screw. Preferably also the pinincludes a cover plug. Advantageously, the means for locating the padagainst the tubular body is located eccentrically or ‘off centre’ to thepad, so that the pad does not spin when being moved.

[0017] According to a second aspect of the present invention, there isprovided a method of supporting a string within tubing in a well bore,the method comprising the steps of:

[0018] mounting a downhole tool, according to the first aspect, onto thestring;

[0019] running the string into the tubing; and

[0020] increasing fluid pressure in an annulus between the string andthe tubing wall, such that the fluid pressure causes moveable pads onthe downhole tool to contact the tubing wall, and thereby anchor thetool to the tubing wall.

[0021] Preferably also the method may include the step of increasing thefluid pressure in the bore of the downhole tool, such that an increasedfluid pressure enters the sleeve through the second outlet, anddisengages the moveable pads from the tubing wall.

[0022] Thus activation and deactivation of the tool can be controlledvia the differential pressure between the annulus and the central boreof the tool.

[0023] An example embodiment of the present invention will now beillustrated with reference to the following Figures, in which:

[0024]FIG. 1 is a downhole tool in accordance with a first embodiment ofthe present invention; and

[0025]FIG. 2 is a cross-sectional view of the downhole tool of FIG. 1taken through the Section A-A.

[0026] Reference is first made to FIG. 1 of the drawings which depicts adownhole tool generally indicated by reference numeral 10. The downholetool 10 has a tubular body 12, which includes a bore 14 passinglongitudinally therethrough. At one end of the tool 10 is a threaded boxsection 16 to connect the tool to adjacent sections of a string (notshown). A complimentary threaded pin 18 is located at the opposite endof the tool 10. The threaded pin 18 provides for connection of the tool10 to adjacent sections of the string below the tool 10. Located againsta shoulder 20 of the tool 10 is a sleeve 22. The arrangement of thesleeve 22 on the body 12 of the tool 10 is more clearly shown in FIG. 2.FIG. 2 being a section A-A through the tool 10 of FIG. 1.

[0027] In FIG. 2 the tubular body 12 has an inner cylindrical surface 24containing the throughbore 14 and an outer cylindrical surface 26. Theouter cylindrical surface 26 is a clearance fit onto the innersubstantially square cross-sectional area of the inner surface 28 of thesleeve 22. The outer surface 30 of the sleeve 22 is substantiallycircular, but includes four indents or grooves 32A-D. The grooves 32A-Densure that fluid can flow past the tool 10 at all times. Mounted on thesleeve 22 are four moveable pads 34A-D. Each pad 34A-D can move radiallyaway from the body 12 to a point at which overhangs 36 on the sleeve and0.38 on the pad connect. It will be appreciated that although onlyindicated at one overhang, the overhangs 36, 38 exist around each of themoveable pads. This is clearly evident in FIG. 1, where the pads areseen to be circular. The outer surface 40 of each pad is an abrasivesurface to provide better contact to the wall of the tubing (not shown).

[0028] To prevent the circular pads 34A-D from spinning, they are bothheld by the overhangs 36, 38 and located on an offset grub screw 42 anda cover plug 44. Each grub screw 42 is attached to the body 12 and thepads 34A-D can slide along the outer edge of the grub screw 42 and coverplug 44. To assist in this the cover plug 44 is made of PTFE.

[0029] Within the tubular body are four radial ports 46 which providefluid contact to the sleeve 22. Where each radial port 46 meets thesleeve 22 there is a passage 48 on the sleeve 22 which allows fluid totravel to a chamber 50 located between the overhangs 36, 38. Within thechamber 50 is located a spring 52 which preferentially holds themoveable pad 34 away from the tubing wall, and against the body 12.

[0030] At the top of the sleeve 22 is a further passage 54 whichprovides an inlet of fluid from the annulus between the tool 10 and thetubing into a chamber 56. Chamber 56 is created in the space between theouter surface 26 of the body 12 and the inner surface 28 of the sleeve22.

[0031] To prevent the ingress of fluid between the sleeve 22 and thebody 12 o-rings 58 are positioned on either side of each of the chambers50, 56.

[0032] In use, the tool is connected on a string via the box section 16and pin section 18. The string is run into the tubing, within awellbore. It will be appreciated, however, that the term ‘tubing’encompasses the common components of casing, liner and the like.

[0033] At a required location, fluid can be pumped through the bore 14of the tool 10. While the fluid pressure in the bore 14 is higher thanthat in the annulus passing the grooves 32 of the sleeve 22, the padsremain closed against the body 12. Thus, the outer surface 26 of thebody 12 contacts the inner surface 28 of the sleeve 22. This is achievedthrough the passage of fluid through the radial port 46, the passage 48and into the chamber 50, and assisted by the action of spring 52.

[0034] However, if the fluid pressure in the annulus increases to apoint to be greater than the fluid pressure within the bore 14, fluidwill enter the passage 54 in the sleeve 22 and fill the chamber 56. Dueto the comparatively large surface area of the inner surface 28 of thesleeve 22, the pads 34 will move rapidly outwards from the body 12. Theouter surface 30 of the pads will contact with the tubing wall andprovide a grip which will anchor the tool 10 against the tubing wall. Inthis position, the tool will bear the weight of the string above thepoint at which it is attached.

[0035] To disengage the tool 10, the fluid pressure in the bore 14 isincreased to a level greater than the fluid pressure in the annulus.When this occurs, the fluid will enter the radial port 46, travelthrough the passage 48 into chamber 50 and separate the overhangs 36,38, moving the pad back against the body 12, to contact the outersurface of the body 26 with the inner surface 28 of the sleeve 22.

[0036] The principal advantage of the present invention is that the toolof the invention can be mounted on a string and run downhole withouthaving any effect on other tools mounted on the same string. Whenrequired, the tool is hydraulically operated and once operated, the toolcan hold up the weight of the string and prevent any weight beingapplied to any tools located on the string below the position of theweight bearing tool.

[0037] A further advantage of the present invention is that the tool maybe engaged or disengaged any number of times within the well bore anddoes not have to be returned to the surface to be reset or reconfigured.

[0038] It will be apparent to those skilled in the art that variousmodifications may be made to the invention herein described, withoutdeparting from the scope thereof. For example, the number of pads may beincreased, their shape or the size of the chambers or reservoirs aroundthem may be changed. Similarly, the tool may be operated by decreasingfluid pressure in the annulus and/or central bore.

1. A downhole tool for connection in a work string to be inserted intotubing in a well bore, the tool comprising a tubular body includingmeans for attachment to the work string, and a sleeve mounted on thetubular body wherein the sleeve includes means to contact a wall of thetubing, such that the tool bears at least a part of a weight of the workstring.
 2. A downhole tool as claimed in claim 1 wherein the means tocontact the tubing wall is a plurality of moveable pads.
 3. A downholetool as claimed in claim 2 wherein the pads are arranged to moveradially with respect to the longitudinal axis of the bore.
 4. Adownhole tool as claimed in claim 2 or claim 3 wherein the tubular bodyincludes one or more radial ports for each moveable pad.
 5. A downholetool as claimed in any preceding claim wherein the sleeve has asubstantially cylindrical outer surface and a substantially squarecross-sectional inner surface.
 6. A downhole tool as claimed in claim 5wherein the sleeve includes one or more grooves positionedlongitudinally on the outer surface.
 7. A downhole tool as claimed inany one of claim 2 to 6 wherein the pads include an abrasive outersurface.
 8. A downhole tool as claimed in any preceding claim whereinthe tool is hydraulically operated.
 9. A downhole tool as claimed in anyone of claims 2 to 8 wherein the moveable pads can be selectivelyactuated to contact the wall of the tubing.
 10. A downhole tool asclaimed in any one of claims 2 to 9 wherein the sleeve includes at leastone port, the port(s) providing access of fluid from the annulus betweenthe tool and the tubing wall to a back surface of the pad.
 11. Adownhole tool as claimed in any one of claims 4 to 10 wherein the sleeveincludes at least one second port, the second port(s) providing accessof fluid between the radial port of the tubular body and a front surfaceof the moveable pad.
 12. A downhole tool as claimed in any one of claims2 to 11 wherein the tool includes means to locate the pads against thetubular body.
 13. A downhole tool as claimed in claim 12 wherein themeans to locate the pads comprises one or more pins there being arespective pin for each pad.
 14. A downhole tool as claimed in claim 12or claim 13 wherein the means for locating the pad against the tubularbody is located eccentrically.
 15. A method of supporting a work stringwithin tubing in a well bore, the method comprising the steps of:mounting a downhole tool including a plurality of moveable pads in thework string; running the work string into the tubing; and increasingfluid pressure in an annulus between the work string and the tubingwall, such that the fluid pressure causes the moveable pads on thedownhole tool to contact the tubing wall, and thereby anchor the tool tothe tubing wall.
 16. The method of claim 15 further including the stepof increasing the fluid pressure in a central bore of the downhole tool,such that the increased fluid pressure causes the moveable pads todisengage from the tubing wall.